Custom ID for RTC work items

This might be an absurd question but I still need to get clarification,
Can I change ID of RTC work item which is generated by server when work item is created?
I think it is not possible to modify system generated id of RTC work item but still I would like to get advice from experts.

This is one of the client requirement where they want to have their own IDs of work items. In every project they want work item's Id count to start from zero.
As per my knowledge we can not do anything with system generated Id? please confirm.
We were wondering if this requirement can be achieved by creating a custom attribute in work item of type small string and develop a custom extension(follow up action) which would set value for this attribute as per client requirement. Using this approach system generated ID's would be untouched preventing any kind of risks that could occur in future(if we perform linking across applications i.e. DNG and RTC and RQM).

Please confirm if we can achieve the task using custom extension or if there is better way to do it.